Speech/Sound Module Q'sbrowsing

I'm attempting to convert speech to text using speech's new recognize function, but when I pass a .m4a audio file (recorded using sound.recorder) through the recognize function, it gives a "corrupt" error. Am I using the wrong kind of audio file or something like that?

which doesn't mention it at all. (I also noticed that sound.play_effect accepts two additional undocumented arguments. I haven't figured out what the fourth does; the fifth appears to cause the sound to loop until stopped if it's anything other than 0.)

Is there additional documentation or a forum post describing sound.Recorder that I'm missing?